Re: [netmod] new YANG 1.1 Issue Y61: I2RS support

[Martin Bjorklund <[e-mail]>]

Andy Bierman <[e-mail]> wrote:
> On Thu, Jul 30, 2015 at 10:41 AM, Martin Bjorklund <[e-mail]> wrote:
> 
> > Andy Bierman <[e-mail]> wrote:
> > > On Wed, Jul 29, 2015 at 10:51 AM, Martin Bjorklund <[e-mail]>
> > wrote:
> > >
> > > > Andy Bierman <[e-mail]> wrote:
> > > > > Hi,
> > > > >
> > > > > I understand the intent is that an implementation of NACM
> > > > > has to understand these NACM extensions.  I agree with Lada
> > > > > that the YANG text about MAY ignore extensions casts doubt whether
> > > > > this sort of NACM rule is enforceable or specified correctly.
> > > >
> > > > So do you agree that it would be a good idea to clarify this
> > > > according to Juergen's suggestion?
> > > >
> > > >
> > > >
> > > Not really.
> > > Pretending the extension is just another description-stmt
> > > does not really fix anything.
> > >
> > > A real YANG statement like config-stmt or a new statement
> > > called ephemeral-stmt can be modified with refine-stmt
> > > or deviate-stmt.   This can never happen for
> > > an external statement.
> >
> > There are two separate issues here:
> >
> > 1) It seems we are in agreement that if a model uses an extension
> >    statement, it is normative (like ietf-system's usage of nacm:*).
> >
> >    Should we somehow clarify this in 6020bis?
> >
> >
> No -- I agree that was the intent, but it is not achievable
> because tools MAY ignore extensions.

But as have been said several times, this was clearly not the
intention.  So we should clarify this in 6020bis.

> > 2) Extensions cannot be refined or deviated.
> >
> >    Actually, the *syntax* rules allows things like:
> >
> >      deviation /x:foo {
> >        deviate replace {
> >          i2rs:ephemeral true;
> >        }
> >      }
> >
> >    I agree that it not clear what this means, but we could also
> >    clarify this in 6020bis.
> >
> >
> > > IMO ephemeral data support needs to be a real statement
> > > that can be used with refine-stmt and  deviate-stmt.
> > > It is a real property of a data node.
> >
> > Note: it is still not clear that such a statement (base or extension)
> > is needed at all.
> >
> >
> 
> I do not understand why you are so opposed to using real YANG statements
> to support ephemeral state.

If this solution was already well defined and agreed upon by everyone,
then it could be done as a YANG statement.  But I am worried that
adding this will take quite some time, and will thus delay YANG 1.1;
and since IMO extensions can be used just as well, there is no real
reason for adding this delay.

> Do you have a better solution that the
> proposal from draft-haas-i2rs-ephermal-state-reqs-00?

Use a separate ephemeral datastore.

> I don't see it.
> I am opposed to using extensions to ephemeral state because
> they are poorly defined in YANG.

Then we should fix this.


/martin

> This is OK since they are for
> defining statements outside the YANG standard.  Normal mechanisms
> like uses/refine and deviate must be supported.
> 
> I do see any advantages whatsoever for using external statements
> instead of YANG statements.